Finger limbs are applied in the field of robotic and/or prosthetic to duplicate the function and/or look of natural, especially human finger limbs. Such finger limbs are movable mounted to a basic element. The basic element hereby serves for the attachment of the finger elements, comprising of the finger limb, to a body part, especially to a hand and or an arm part. An electric motor is used for movement of the finger limb relative to the basic element. Hereby, the electric motor can be positioned in the finger limb or outside of the finger limb, for instance at or in the basic element.
If the finger limb needs to be moved, an electric motor, designed as a DC motor, as an electrically commutated motor, or a stepper motor, is supplied with a continuous or pulsed current so that the output shaft moves, especially pivots, the finger limb via a transmission such as a planetary gear, a spur gear, a bevel gear, and/or a worm gear, a head screw, a friction gear transmission and/or through driving rods, belts and/or chains.
There are, however, situations in which the finger limb needs to be maintained in a position. This holding can take place against an outer force as it happens during the holding of a holding rod, whereby the weight of the person during the holding moves into the hand. It can also be desired to maintain a position without having a significant external force affecting the finger and/or the finger limb.
EP 0748194 shows a finger element in which the movement of the electric motor is transferred, via a worm gear transmission, to a pivoting movement of the finger limb. The intention is to create a self locking for keeping the finger in its position even against an outside force.
Known through EP 0748 194 B1 is an electrically operated hand prosthesis in which the drive motor, which moves the finger, is positioned in the finger. In accordance with the approach to the solution which is discussed here, the motor axle has a worm shaft which meshes with a respective worm gear wheel which is stationary positioned in the support body of the prosthesis. The proposed worm gear wheel/worm shaft combination has the alleged advantage that this transmission is a locking transmission in which the finger is locked in its position without a motor drive.
EP 1962731 and EP 2135588 show a finger limb in which a worm gear transmission is applied for self locking, whereby the worm gear wheel is linked to the basic element via a bevel gear transmission.